NMR in Biomedicine
1099-1492
0952-3480
Anh Quốc
Cơ quản chủ quản: John Wiley and Sons Ltd , WILEY
Lĩnh vực:
SpectroscopyRadiology, Nuclear Medicine and ImagingMolecular Medicine
Phân tích ảnh hưởng
Thông tin về tạp chí
NMR in Biomedicine is a journal devoted to the publication of original full-length papers, rapid communications and review articles describing the development of magnetic resonance spectroscopy or imaging methods or their use to investigate physiological, biochemical, biophysical or medical problems. Topics for submitted papers should be in one of the following general categories: (a) development of methods and instrumentation for MR of biological systems; (b) studies of normal or diseased organs, tissues or cells; (c) diagnosis or treatment of disease. Reports may cover work on patients or healthy human subjects, in vivo animal experiments, studies of isolated organs or cultured cells, analysis of tissue extracts, NMR theory, experimental techniques, or instrumentation.
Các bài báo tiêu biểu
<sup>31</sup>P NMR spectroscopic and near infrared spectrophotometric studies of effects of anesthetics on <i>In vivo</i> RIF‐1 tumors. relationship to tumor radiosensitivity Abstract Mice with subcutaneous RIF‐1 tumors were anesthetized with sodium pentobarbital (PB) or ketamine plus acepromazine (KA) before acquisition of in vivo 31 P nuclear magnetic resonance (NMR) spectra from tumors. The area of the inorganic phosphate resonance was significantly greater (relative to phosphomonoesters or the α‐phosphate resonance of nucleoside triphosphate) in spectra obtained under PB anesthesia, suggesting that the hypoxic fraction of the tumor increased following PB anesthesia. In vivo near‐infrared laser spectroscopy directly demonstrated that tumor oxyhemoglobin was reduced by more than 20% following PB but was not significantly affected by KA. Total hemoglobin (tumor blood volume) was reduced by 11% following PB anesthesia, but was not significantly affected by KA. Tumor growth delay induced by γ‐irradiation was shorter when tumors were irradiated under PB anesthesia than when irradiated under KA, showing that PB anesthesia had a radioprotective effect. These studies demonstrate that both the 31 P NMR and near infrared methods can detect metabolic or physiological changes associated with an increase in tumor radioresistance (i.e., an increase in the radiobiological hypoxic fraction).
Tập 2 Số 3 - Trang 87-92 - 1989
Time‐dependent effects of anesthetic agents on <sup>31</sup>P NMR high‐energy phosphates in KHT and RIF‐1 fibrosarcomas Abstract Previous studies have reported significant radiobiological and hemodynamic effects associated with sodium pentobarbital (PB) anesthetization. The present work contrasts the effects of PB with azaperone‐ketamine (AZ) in RIF‐1 and KHT tumors while animal body core temperature is maintained at 37 °C. The primary aims were to evaluate both agents in terms of: (i) duration of anesthetic; (ii) effect on absolute levels of 31 P NMR phosphocreatine (PCr) + β‐nucleoside triphosphate (β‐NTP)/inorganic phosphate (Pi ) ratios; and (iii) effect on temporal variability of PCr+β‐NTP/Pi ratios. In terms of overall duration, AZ was the clear preference. Although the maintenance of 37 °C core temperature significantly reduced overall durations for both anesthetics, AZ animals invariably remained immobile for a minimum of 80 min. For PB, durations were highly unpredictable. With AZ, mean PCr + β‐NTP/Pi ratios were constant over the entire 80 min period for both lines. With PB, PCr + β‐NTP/Pi ratios were lower in relation to AZ for KHT at select timepoints, but highly variable among RIF‐1 tumours. Since ratios under PB varied substantially with time for RIF‐1 lines, measurements taken with PB are clearly not representative of the control state. Furthermore, in light of the consistent and reproducible results obtained with AZ, this anesthetic is considered a marked improvement over PB for animal studies of this nature.
Tập 4 Số 3 - Trang 137-141 - 1991
Comparison of pH measurements made using <sup>31</sup>P NMR and a fibreoptic pH meter Abstract The objective of this study was to compare pH measurements made in biological samples using 31 P NMR (pHNMR ) with those made with a novel, dye‐based fibreoptic pH measurement system (pHF ), which is compatible with use in electromagnetic fields without field perturbation. Using protein‐free model solutions, pHNMR was calibrated against pHF , giving a correlation coefficient of 0.969 and a mean difference (± SD) between pHNMR and pHF of 0.037±0.054 over the pH range 6.8–7.7. Further calibration of pHNMR with pHF was carried out for human red blood lysates and then pHNMR was compared with pHF for whole, packed red blood cells over the pH range 7.0–7.8. Values for pHNMR , the intracellular pH, were consistently lower than for pHF , the extracellular pH, by a mean (±SD) of 0.15±0.02 units. A close correlation of extracellular pHNMR with pHF was demonstrated for a blood sample exhibiting two Pi peaks, over the pH range 7.03–7.71. We conclude that concurrent use of NMR and the fibreoptic pH meter provides a reliable method of simultaneous measurement of intracellular and extracellular pH in biological systems.
Tập 5 Số 6 - Trang 360-363 - 1992
Automatic quantitation of localized <i>in vivo</i><sup>1</sup>H spectra with LCModel Abstract The LCModel method analyzes an in vivo spectrum as a Linear Combination of Model in vitro spectra from individual metabolite solutions. Complete model spectra, rather than individual resonances, are used in order to incorporate maximum prior information into the analysis. A nearly model‐free constrained regularization method automatically accounts for the baseline and lineshape in vivo without imposing a restrictive parameterized form on them. LCModel is automatic (non‐interactive) with no subjective input. Approximately maximum‐likelihood estimates of the metabolite concentrations and their uncertainties (Cramér‐Rao lower bounds) are obtained. LCModel analyses of spectra from users with fields from 1.5 to 9.4 T and a wide range of sequences, particularly with short TE , are used here to illustrate the capabilities and limitations of LCModel and proton MRS. Copyright © 2001 John Wiley & Sons, Ltd.
Abbreviations used:
Ala
alanine
Asp
aspartate
Cr
creatine
GABA
γ‐aminobutyric acid
Glc
glucose
Gln
glutamine
Glu
glutamate
GPC
glycerophosphocholine
GSH
glutathione
Ins
myo ‐inositol
Lac
lactate
NAA
N ‐acetylaspartate
NAAG
N ‐acetylaspartylglutamate
PC
phosphocholine
PCr
phosphocreatine
PE
phosphoethanolamine
Scyllo
scyllo ‐inositol
S/N
signal‐to‐noise ratio
Tau
taurine.
Tập 14 Số 4 - Trang 260-264 - 2001
Biochemical considerations in <sup>1</sup>H spectroscopy. Glutamate and glutamine; <i>Myo</i>‐inositol and related metabolites Abstract Glutamate and glutamine, which can be clearly identified and, in part, quantified in proton spectra of the brain, play important roles in normal and pathological biochemistry. Pathways of glutamate metabolism include transamination, dehydrogenation, deamination and decarboxylation (to GABA). Glutamine is notable in hepatic encephalopathy, but is also a significant metabolic fuel in several other organs and tissues, including neoplasms. Myo ‐inositol is a 6‐carbon alcohol which acquires new interest from its detection and quantitation in 1 H spectra. Its role, apart from a biochemical relationship to messenger‐inositol polyphosphates, is unclear.
Tập 4 Số 2 - Trang 59-63 - 1991
Wall shear stress calculations based on 3D cine phase contrast MRI and computational fluid dynamics: a comparison study in healthy carotid arteries Wall shear stress (WSS) is involved in many pathophysiological processes related to cardiovascular diseases, and knowledge of WSS may provide vital information on disease progression. WSS is generally quantified with computational fluid dynamics (CFD), but can also be calculated using phase contrast MRI (PC‐MRI) measurements. In this study, our objectives were to calculate WSS on the entire luminal surface of human carotid arteries using PC‐MRI velocities (WSSMRI ) and to compare it with WSS based on CFD (WSSCFD ). Six healthy volunteers were scanned with a 3 T MRI scanner. WSSCFD was calculated using a generalized flow waveform with a mean flow equal to the mean measured flow. WSSMRI was calculated by estimating the velocity gradient along the inward normal of each mesh node on the luminal surface. Furthermore, WSS was calculated for a down‐sampled CFD velocity field mimicking the MRI resolution (WSSCFDlowres ). To ensure minimum temporal variation, WSS was analyzed only at diastole. The patterns of WSSCFD and WSSMRI were compared by quantifying the overlap between low, medium and high WSS tertiles. Finally, WSS directions were compared by calculating the angles between the WSSCFD and WSSMRI vectors. WSSMRI magnitude was found to be lower than WSSCFD (0.62 ± 0.18 Pa versus 0.88 ± 0.30 Pa, p < 0.01) but closer to WSSCFDlowres (0.56 ± 0.18 Pa, p < 0.01). WSSMRI patterns matched well with those of WSSCFD. The overlap area was 68.7 ± 4.4% in low and 69.0 ± 8.9% in high WSS tertiles. The angles between WSSMRI and WSSCFD vectors were small in the high WSS tertiles (20.3 ± 8.2°), but larger in the low WSS tertiles (65.6 ± 17.4°). In conclusion, although WSSMRI magnitude was lower than WSSCFD , the spatial WSS patterns at diastole, which are more relevant to the vascular biology, were similar. PC‐MRI‐based WSS has potential to be used in the clinic to indicate regions of low and high WSS and the direction of WSS, especially in regions of high WSS. Copyright © 2014 John Wiley & Sons, Ltd.
Tập 27 Số 7 - Trang 826-834 - 2014
Diffusion tensor imaging detects treatment effects of FTY720 in experimental autoimmune encephalomyelitis mice Fingolimod (FTY720) is an orally available sphingosine‐1‐phosphate (S1P) receptor modulator reducing relapse frequency in patients with relapsing–remitting multiple sclerosis (RRMS). In addition to immunosuppression, neuronal protection by FTY720 has also been suggested, but remains controversial. Axial and radial diffusivities derived from in vivo diffusion tensor imaging (DTI) were employed as noninvasive biomarkers of axonal injury and demyelination to assess axonal protection by FTY720 in experimental autoimmune encephalomyelitis (EAE) mice. EAE was induced through active immunization of C57BL/6 mice using myelin oligodendrocyte glycoprotein peptide 35–55 (MOG35–55 ). We evaluated both the prophylactic and therapeutic treatment effect of FTY720 at doses of 3 and 10 mg/kg on EAE mice by daily clinical scoring and end‐point in vivo DTI. Prophylactic administration of FTY720 suppressed the disease onset and prevented axon and myelin damage when compared with EAE mice without treatment. Therapeutic treatment by FTY720 did not prevent EAE onset, but reduced disease severity, improving axial and radial diffusivity towards the control values without statistical significance. Consistent with previous findings, in vivo DTI‐derived axial and radial diffusivity correlated with clinical scores in EAE mice. The results support the use of in vivo DTI as an effective outcome measure for preclinical drug development. Copyright © 2013 John Wiley & Sons, Ltd.
Tập 26 Số 12 - Trang 1742-1750 - 2013
The basis of anisotropic water diffusion in the nervous system – a technical review Abstract Anisotropic water diffusion in neural fibres such as nerve, white matter in spinal cord, or white matter in brain forms the basis for the utilization of diffusion tensor imaging (DTI) to track fibre pathways. The fact that water diffusion is sensitive to the underlying tissue microstructure provides a unique method of assessing the orientation and integrity of these neural fibres, which may be useful in assessing a number of neurological disorders. The purpose of this review is to characterize the relationship of nuclear magnetic resonance measurements of water diffusion and its anisotropy (i.e. directional dependence) with the underlying microstructure of neural fibres. The emphasis of the review will be on model neurological systems both in vitro and in vivo . A systematic discussion of the possible sources of anisotropy and their evaluation will be presented followed by an overview of various studies of restricted diffusion and compartmentation as they relate to anisotropy. Pertinent pathological models, developmental studies and theoretical analyses provide further insight into the basis of anisotropic diffusion and its potential utility in the nervous system. Copyright © 2002 John Wiley & Sons, Ltd.
Tập 15 Số 7-8 - Trang 435-455 - 2002
Enhanced sensitivity with fast three‐dimensional blood‐oxygen‐level‐dependent functional MRI: comparison of SENSE–PRESTO and 2D‐EPI at 3 T Abstract A major impetus in functional MRI development is to enhance sensitivity to changes in neural activity. One way to improve sensitivity is to enhance contrast to noise ratio, for instance by increasing field strength or the number of receiving coils. If these parameters are fixed, there is still the possibility to optimize scans by altering speed or signal strength [signal‐to‐noise ratio (SNR)]. We here demonstrate a very fast whole‐brain scan, by combining a three‐dimensional (3D)‐PRESTO (principle of echo shifting with a train of observations) pulse sequence with a commercial eight‐channel head coil and sensitivity encoding (SENSE). 3D‐PRESTO uses time optimally by means of echo shifting. Moreover, 3D scans can accommodate SENSE in two directions, reducing scan time proportionally. The present PRESTO–SENSE sequence achieves full brain coverage within 500 ms. We compared this with a two‐dimensional (2D) echo planar imaging (EPI) scan with identical brain coverage on 10 volunteers. Resting‐state temporal SNR in the blood‐oxygen‐level‐dependent (BOLD) frequency range and T‐statistics for thumb movement and visual checkerboard activations were compared. Results show improved temporal SNR across the brain for PRESTO–SENSE compared with EPI. The percentage signal change and relative standard deviation of the noise were smaller for PRESTO–SENSE. Sensitivity for brain activation, as reflected by T‐values, was consistently higher for PRESTO, and this seemed to be mainly due to the increased number of observations within a fixed time period. We conclude that PRESTO accelerated with SENSE in two directions can be more sensitive to BOLD signal changes than the widely used 2D‐EPI, when a fixed amount of time is available for functional MRI scanning. Copyright © 2008 John Wiley & Sons, Ltd.
Tập 21 Số 7 - Trang 663-676 - 2008
Clinical ultrashort echo time imaging of bone and other connective tissues Abstract The background underpinning the clinical use of ultrashort echo time, SPRITE and other pulse sequences for imaging bone and other connective tissues with short T 2 is reviewed. Features of the basic physics relevant to UTE imaging are described, including the consequences when the radiofrequency pulse duration is of the order of T 2 so that rotation of tissue magnetization into the transverse plane is incomplete. Consequences of the broad linewidth of short T 2 components are also discussed, including partial saturation by off‐resonance fat suppression pulses as well as those used in multislice and multiecho imaging. The need for rapid data acquisition of the order of T 2 is explained. The basic two‐dimensional UTE pulse sequence with its half excitation pulse and radial imaging from the centre of k ‐space is described, together with options that suppress fat and/or reduce the signal from long T 2 components. The basic features of SPRITE and other sequences with very short TE are described. Image interpretation is discussed. Clinical features of the imaging of cortical bone, tendons, ligaments, menisci, periosteum and the spine are illustrated. The source of the short T 2 signal in these tissues is predominantly collagen and water tightly bound to collagen. Short T 2 components in all of these tissues are detectible and may show high signals. Possible future developments are outlined, as are technical limitations of clinical magnetic resonance systems. Copyright © 2006 John Wiley & Sons, Ltd.
Tập 19 Số 7 - Trang 765-780 - 2006